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Old Pass Labs X150 or FirstWatt F8 (Atalante 3 speakers)?

C

CharlieAudio

Active Member
The Atalante 3 speakers are similar in size to the Spendor Class 3/1. The listening room is just under 4 by 6 meters. Moderate listening volume, classical music.

Is there a significant difference to expect from a FirstWatt F8, a Class A amplifier rated at 25 watts into 8 ohms, and one of the old original Pass Labs X150 amplifiers in good condition, rated at 150 watts of which about 25 watts are in Class A?
 
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Your speakers are about 85.5 dB sensitivity per the 1 watt/1meter standard, a little on the low side. The X150 might be a better match since it is more powerful.
 
I run a Firstwatt kit amp, and in this case I too would choose the X150

Please post up photos when you move forward so we can drool and fawn :)
 
Thanks for the advice about headroom. The damping factors are different, too: F8 - 40, X150 - 250.

This is a comparison of the commercial F8 (product photo), the latest in Nelson Pass's series of FirstWatt amps, not a kit, with the X150.

If people have experience with one or both of these, great to weigh in.


FirstWattF8_front_and_rear.jpg
 
F8 is capacitor coupled output likely contributing to lower DF. But, even at 40 or whatever isn't all that big a deal. And, power in 4 ohms is less than 8 ohms, if that matters in your use.
 
A couple of questions
How loud to you want to play?
And how hard are your loudspeaker to drive? Mostly interested in impedance variations phase angels.
 
mad shadows said:
A couple of questions
How loud to you want to play?
And how hard are your loudspeaker to drive? Mostly interested in impedance variations phase angels.
Click to expand...

I play at moderate volume in the 4 x 6 meter room. I like to hear sound, not feel bass in my body.
The speakers:
Nominal Impedance 6 ohms
Minimum Impedance 4 ohms at 175Hz
Sensitivity (2.83V/1m) 87dB/2.83V/1metre
Crossover Frequency 2.8 kHz
Recommended Amplifier Power Power handling: 150 watts, starting from 30 watts.
Recommended Room Size 15 to 35 m2
per bestofhighend.com/revival-audio-atalante-3-review/

I've looked around the Web for a graph of impedance across frequencies but have not found one.
 
CharlieAudio said:
If people have experience with one or both of these, great to weigh in.
Click to expand...

I've had a Pass x150 for three or four years and it's a very good, quiet, capable amplifier. I used it to drive 4 ohm speakers rated at 89 db with no issues. After about 30 minutes to warm up I could listen for hours. Never heard it strain at any listening level.

The Pass and First Watt amps are significantly different amps, though. The Pass is biased so the first watts are in Class A and then it continues to deliver power up to 150 watts or more depending on speaker impedance. Pass amps are designed to deliver plenty of power and to handle challenging speaker loads. With the Pass Labs x150 when speaker impedance goes down, the power output of the amplifier goes up.

The First Watt amps are a passion project for Nelson Pass and are an outlet for him to explore other design ideas. Generally speaking they are designed to deliver modest power, remain in Class A, and drive more efficient speaker loads. With the First Watt F8, as speaker impedance goes down, power output from the amp goes down as well.

The folks at Pass are very responsive to questions - even about their legacy products. If you drop them an email I'm sure they'll get back to you quickly.
 
dcmfan said:
The folks at Pass are very responsive to questions - even about their legacy products. If you drop them an email I'm sure they'll get back to you quickly.
Click to expand...

So I asked the people at Pass Labs, letting them know I have a FirstWatt F8 and was considering the original Pass X150. From the reply: "The X150 will have more power but it doesn't have the sonic signature of the F8, not even close. An XA30.5 has a similar sound to the F8 with more power into 4 ohms."

Persuasive to me. Incidentally, when I asked via the webmail dialog on their website, I got no answer after almost two weeks. Then I used an actual email to the company and got a reply within a day.
 
CharlieAudio said:
An XA30.5 has a similar sound to the F8 with more power into 4 ohms.
Click to expand...

I was going to suggest the 30.x amplifiers but didn't want to muddy the waters. Glad they got back to you!

Didn't realize you already had the F8, so I'm curious - how is it driving your speakers now? Anything you wish were different?
 
dcmfan said:
... how is it driving your speakers now?
Click to expand...

At a couple of weeks together, the FirstWatt F8 and Atalante 3's are a great combination. The usual adjectives: musical; accurate across bass, mids, and treble; plenty of detail and presence.

Because of the layout in the room, I put the supplied foam plugs in the rear ports, but not completely, just enough to keep them in ... which is almost all the way, because otherwise a bass pulse at medium volume will blow them to the floor!

I'd like to find an impedance curve for the Atalante 3. A frequency response curve shows dips at 70 and 180 Hz.
 
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